[PATCH 5.10 006/406] modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules

Greg Kroah-Hartman
2023-09-17T19:18:18Z

From: Christoph Hellwig <hch@lst.de>

commit 9011e49d54dcc7653ebb8a1e05b5badb5ecfa9f9 upstream.

It has recently come to my attention that nvidia is circumventing the
protection added in 262e6ae7081d ("modules: inherit
TAINT_PROPRIETARY_MODULE") by importing exports from their proprietary
modules into an allegedly GPL licensed module and then rexporting them.

Given that symbol_get was only ever intended for tightly cooperating
modules using very internal symbols it is logical to restrict it to
being used on EXPORT_SYMBOL_GPL and prevent nvidia from costly DMCA
Circumvention of Access Controls law suites.

All symbols except for four used through symbol_get were already exported
as EXPORT_SYMBOL_GPL, and the remaining four ones were switched over in
the preparation patches.

Fixes: 262e6ae7081d ("modules: inherit TAINT_PROPRIETARY_MODULE")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/module.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2268,15 +2268,26 @@ static void free_module(struct module *m
void *__symbol_get(const char *symbol)
{
struct module *owner;
+ enum mod_license license;
const struct kernel_symbol *sym;

preempt_disable();
- sym = find_symbol(symbol, &owner, NULL, NULL, true, true);
- if (sym && strong_try_module_get(owner))
+ sym = find_symbol(symbol, &owner, NULL, &license, true, true);
+ if (!sym)
+ goto fail;
+ if (license != GPL_ONLY) {
+ pr_warn("failing symbol_get of non-GPLONLY symbol %s.\n",
+ symbol);
+ goto fail;
+ }
+ if (strong_try_module_get(owner))
sym = NULL;
preempt_enable();

return sym ? (void *)kernel_symbol_value(sym) : NULL;
+fail:
+ preempt_enable();
+ return NULL;
}
EXPORT_SYMBOL_GPL(__symbol_get);